It is priorly known to transmit optical signals through light transmission paths comprised of optical fibers. For generating the optical signals laser diodes and monitor diodes have been combined to form laser modules that control the optical signals generated. The employment of monitor diodes in association with regulators control the efficiency of the laser diodes in such laser modules. Without such employment of the monitor diodes, the control of the efficiency of the laser diodes is extremely difficult and complex, both as to circuitry and expense. Deviations in the generation of optical signals of the laser diodes caused by manufacturing variations, as well as temperature and aging influences, may be obviated by the regulation provided by the monitor diodes.
British Patent Application 2,000,373 is directed to diodes that function alternately as emitters and detectors of light of the same wave length. It is known to make diodes which, when biased in the forward direction, are capable of emitting light rays in a certain frequency band and, which, when biased in the backward direction, are capable, when exposed to the same rays, of generating electrical signals in response. In this prior art reference there is disclosed an optical fiber telecommunication system wherein first and second diodes are connected at opposite ends of an optical transmission fiber for alternating transmissions. When the first diode is biased in the forward direction, the second is biased in the backward direction and the system functions in the direction of the first diode to the second; and in the opposite case, the system functions in the direction of the second diode to the first diode. Accordingly, such diodes can be alternately switched from transmitter to receiver, depending upon the desired direction of transmissions during specific intervals of time.
Light diode circuits for half duplex operations are priorly known for transmitting optical signals through optical fibers. In such circuits the same light diodes are used as transmitters as well as receivers. When operating as receivers, such known circuits operate at low efficiencies since the light diodes are configured as transmitting diodes and not as receiving diodes. Consequently, the transmission of optical signals through the optical fibers is limited to short distances. Further, the use of such known circuits, because of such low efficiencies, are inappropriate for the transmission of information technology with associate high BIT rates.
Light transmitting semiconductor elements employed simultaneously both as optical transmitters and receivers are also priorly known. However, such semiconductor elements can convert the received signals only with low efficiency because their structures are configured appropriately for transmitting only and, accordingly, suitable for only short distance transmissions.